In mammalian organisms, nine monosaccharide building blocks are used to form cell-surface complex, higher order glycans that mediate cell-cell communication during development processes and differentiation programs. By contrast, aberrant glycosylation signals the onset of cancer. What directs pathogenic glycosylation? Is there a correlation between glycosylation patterns and cancer progression? Can we manipulate differentiation by changing the glycan coat? Despite forty years of glycobiology research, the answers to these questions remain obscure. Dynamic changes in glycosylation during many developmental processes and cancer progression are still poorly characterized. Because peripheral, higher order glycans encode information for cell-surface receptor recognition to trigger specific downstream signaling, there is an urgent and unmet need to develop methods for their detection. The long-term objective of this project is to develop chemoenzymatic methods for the specific labeling of cell-surface higher-order glycans with small-molecule biophysical probes for their characterization. To achieve this goal is to transform glycosylation enzymes into labeling reagents to target cell-surface specific glycans. Our central hypothesis is that chemoenzymatic methods for glycan detection in cells and tissue samples will have superior specificity and sensitivity than lectin- and antibody-based techniques, the current gold standard for glycan detection. In Aim 1, we will develop chemoenzymatic methods for the labeling of four sectors of glycans on the surface of live mammalian cells and transform these methods into histological techniques to label glycans in tissue sections. In Aim 2, we the small intestine developmental process. We will use the methods developed in Aim 1 to characterize the epithelial will use as a model system to study the role of glycans in a glycosylation patterns in this system. We will investigate the contribution of glycan-lectin interactions to the highly regulated cell migration and maturation in this compartment. Finally, we will apply the chemoenzymatic methods to screen cancer-associated glycans in lung resection samples from patients diagnosed with lung adenocarcinoma (Aim 3). Our goal is to investigate the potential role of these glycans in the evolution of lung cancer, and to pilot test their clinical utility forearly lung cancer detection.